Guide sheaths that facilitate insertion of in vivo devices in general, and electrode leads in particular, are known in the art. Since the insertion and the placement of a lead by itself is complicated due to the flexibility of the device and the contractility of the body lumens, the lead is usually inserted through a stiff guide sheath that is inserted into the body lumen ahead of the lead insertion. The complexity of inserting leads is further enhanced when the lead is inserted into veins due to particular problems that will be comprehensively explained herein after.
Several particular treatment methods in which the insertion of a lead is required, faces additional difficulties. For example, several devices require the delivery of electric signals to the left ventricle of the heart. In PCT/IL97/00012, published as WO 97/25098, titled ELECTRICAL MUSCLE CONTROL (Ben-Haim et al.), a lead is used for the delivery of contractility modulation non-excitatory signals to the left ventricle surface. In PCT/IL99/00392, published as WO 00/04947, titled PACING WITH HEMODYNAMIC ENHANCEMENT (Darvish et al.), one or more electrodes are used for respective cardiac muscle segments pacing with hemodynamic improvement. The placement of the electrode lead is very important in cases such as these, hence the placement of such leads on the surface of the left ventricle is desirable. A method that allows placing the electrode lead on the surface of the left ventricle involves the insertion of the lead to a vein reaching the right atrium and inserting it to the coronary sinus, which is the drain of the coronary veins. Through the coronary veins, it is possible to place the lead on top of the left ventricle surface.
Other methods are available for treating hemodynamic disfunction. An example for such method in which insertion of electrode lead into the coronary veins is advantageous, is biventricular pacing. Examples for the use of biventricular pacing are widely available and in the patent literature, an example is disclosed in U.S. Pat. No. 4,928,688 “METHOD AND APPARATUS FOR TREATING HEMODYNAMIC DISFUCTION” filed in 1989 by Mower, in which hemodynamic disfunction is treated by simultaneously pacing both ventricles of the heart.
Inserting electrode leads into the coronary veins faces several additional difficulties, as follows:    1. Chronic leads are designed so that maximum flexibility is allowed. Flexible electrode lead cannot be forcibly pushed through lumens, especially through veins that are frequently contracted.    2. The coronary veins tend to get narrow towards the apex of the chamber. When there is a need to insert the lead to the vicinity of the apex, the vein itself will impose a considerable resistance to the insertion of the lead. Moreover, the coronary veins become especially tortuous in the vicinity of the coronary sinus so that maneuvering in the veins becomes impossible.    3. The blood in the veins flows towards the coronary sinus so the flow of blood opposite the direction of the lead insertion interferes with the insertion of the lead and pushes the lead itself outwardly.As the accuracy in the lead placement becomes essential, these problems encountering the lead insertion are intensified.